CN110691948B

CN110691948B - Air conditioning system

Info

Publication number: CN110691948B
Application number: CN201880036734.1A
Authority: CN
Inventors: 中川裕介; 小岛诚; 山田拓郎
Original assignee: Daikin Industries Ltd
Current assignee: Daikin Industries Ltd
Priority date: 2017-07-20
Filing date: 2018-07-13
Publication date: 2021-08-17
Anticipated expiration: 2038-07-13
Also published as: EP3657090A4; WO2019017299A1; US11371743B2; JP6783271B2; EP3657090A1; US20200141609A1; AU2018302611A1; AU2018302611B2; JP2019020112A; CN110691948A

Abstract

The invention provides an air conditioning system which suppresses noise in connection with gas-liquid two-phase conveyance. An air conditioning system (100) performs a refrigeration cycle in a Refrigerant Circuit (RC) that includes an outdoor unit (10), a plurality of indoor units (40), and a liquid-side communication pipe (LC). The air conditioning system (100) is provided with an outdoor second control valve (17, an electrically operated valve) that reduces the pressure of the refrigerant flowing through the Refrigerant Circuit (RC) according to the degree of opening, an operating capacity fluctuation detection unit (74, a detection unit) that detects changes in the number of operating units based on equipment information, and an equipment control unit (75) that controls the state of the outdoor second control valve (17). When a change in the number of operating units is detected by an operating capacity variation detection unit (74), an equipment control unit (75) executes feed-forward control (first control) to adjust the opening of an outdoor second control valve (17) so as to suppress an increase in the pressure of refrigerant flowing into the operating units.

Description

Air conditioning system

Technical Field

The present invention relates to an air conditioning system.

Background

Currently, there is known an air conditioning system having an outdoor unit and a plurality of indoor units. For example, patent document 1 (international publication No. 2015/029160) discloses an air conditioning system in which one outdoor unit and a plurality of indoor units are connected via refrigerant communication pipes. In patent document 1, an expansion valve (indoor expansion valve) is disposed in each indoor unit, and the refrigerant is decompressed by the indoor expansion valve during the cooling operation.

Disclosure of Invention

Problems to be solved by the invention

In an air conditioning system, when the operating state of a plurality of indoor units changes greatly (i.e., when the operating capacity changes greatly), the pressure of the coolant flowing into the operating indoor unit increases instantaneously, and in association with this, the amount of pressure reduction of the indoor expansion valve increases, and noise may be generated. Provided is an air conditioning system that suppresses noise.

Means for solving the problems

The air conditioning system according to the first aspect performs a refrigeration cycle in the refrigerant circuit. The refrigerant circuit includes an outdoor unit, a plurality of indoor units, and refrigerant communication piping. The refrigerant communication pipe connects the outdoor unit and the indoor unit. The air conditioning system according to the first aspect includes an electrically operated valve, a detection unit, and a control unit. The electric valve reduces the pressure of the refrigerant flowing through the refrigerant circuit according to the opening degree. The detection unit detects a change in the number of operating units, which are indoor units in an operating state. The control unit controls the state of the electric valve. The control unit executes a first control when the detection unit detects a change in the number of the operating units. The control unit adjusts the opening degree of the motor-operated valve in the first control so as to suppress an increase in the pressure of the refrigerant flowing into the operation unit.

In the air conditioning system according to the first aspect, when the detection unit detects a change in the number of the operation units, the control unit executes a first control in which the opening degree of the electrically operated valve is adjusted so as to suppress an increase in the pressure of the refrigerant flowing into the operation units. Thus, when the number of operating units of the indoor unit changes, the increase in the pressure of the refrigerant flowing into the operating unit is suppressed by adjusting the opening degree of the predetermined motor-operated valve. As a result, noise increase in the operation unit is suppressed.

The "operation stop state" herein includes not only a state in which the operation of the indoor unit is completely stopped (a state in which the operation is stopped by an instruction input to the remote controller, or the like), but also a state in which the operation is suspended (a state in which the operation is suspended due to a thermal shutdown or the like).

The "electrically operated valve" herein is an electronic expansion valve that suppresses an increase in the pressure of the refrigerant flowing into the operation means by adjusting the opening degree in the first control, and the arrangement location and number thereof are not particularly limited.

The "detection unit" detects a change in the number of operating units, which are indoor units in an operating state, based on predetermined information (for example, a signal specifying that the indoor units are in a stopped operating state transmitted from the indoor units or a remote controller, or variables such as refrigerant pressure and refrigerant temperature on the low-pressure side in the refrigeration cycle) that can determine a change in the number of operating units.

An air conditioning system according to a second aspect is the air conditioning system according to the first aspect, wherein the refrigerant flowing from the outdoor unit to the indoor unit is sent in a gas-liquid two-phase state. Thus, even when the operation capacity is changed greatly (due to a large change in the operation state of the plurality of indoor units) when the gas-liquid two-phase conveyance is performed in which the opening degree of the indoor expansion valve is increased, it is possible to suppress a momentary increase in the decompression amount of the indoor expansion valve, as compared with the case of performing the liquid conveyance. Therefore, the increase in noise in the operation unit in connection with the gas-liquid two-phase conveyance is suppressed.

The air conditioning system according to a third aspect is the air conditioning system according to the first or second aspect, wherein the control unit executes the first control when the detection unit detects that the number of the operating units decreases. In the air conditioning system according to the third aspect, when the detection unit detects that the number of operating units is reduced, the control unit executes the first control, and such a situation is suppressed.

An air conditioning system according to a fourth aspect is the air conditioning system according to any one of the first to third aspects, further including a storage unit. The storage unit stores capability information. The capability information is information that specifies the air conditioning capability of each indoor unit. The control unit executes a first control when the detection unit detects a change in the number of the operating units. The first state is a state in which the total value of the air conditioning capacities of the indoor units whose operating states have changed is equal to or greater than a predetermined reference value.

Thus, when the detection unit detects a change in the number of operating units, the control unit executes the first control when the indoor unit is in the first state (the state in which the total value of the air conditioning capacities of the indoor units whose operating states have changed is equal to or greater than a predetermined reference value). That is, whether to execute the first control is determined in consideration of the magnitude of the air conditioning capacity of the indoor unit whose operation state has changed, in addition to the change in the number of operating units. As a result, when the operating capacity of the entire system changes greatly (that is, when the first control is very necessary to be executed), the first control can be executed reliably. Therefore, the increase in noise in the operation unit is more reliably suppressed.

Here, "air conditioning capacity" is a value (kW) indicating a heat load handling capacity of the indoor unit during operation, such as cooling capacity, and is converted to horsepower.

The "reference value" is a value that assumes that the operating capacity has varied to such an extent that noise is likely to increase in the operating means, and is set as appropriate in accordance with design specifications and installation environments.

An air conditioning system according to a fifth aspect is the air conditioning system according to any one of the first to fourth aspects, wherein the electrically operated valve is a first electrically operated valve. The first motor-operated valve decompresses the refrigerant so that the refrigerant flowing from the outdoor unit to the indoor unit passes through the refrigerant communication pipe in a gas-liquid two-phase state. Thus, in the first control, the opening degree of the first motor-operated valve is adjusted, and the pressure increase of the refrigerant flowing into the operation unit is accurately and easily suppressed. Therefore, cost control can be achieved while suppressing, with high accuracy, an increase in noise in the operation unit associated with the gas-liquid two-phase conveyance.

The "first motor-operated valve" herein is an "electronic expansion valve" that decompresses the refrigerant so that the refrigerant flowing from the outdoor unit into the indoor unit passes through the refrigerant communication pipe in a gas-liquid two-phase state, and the location and number of the "first motor-operated valves" are not particularly limited as long as the increase in the pressure of the refrigerant flowing into the operation unit can be suppressed by adjusting the opening degree in the first control.

An air conditioning system according to a sixth aspect is the air conditioning system according to any one of the first to fifth aspects, wherein the electrically operated valve is a second electrically operated valve. The second motor-operated valve reduces the pressure of the refrigerant flowing from the refrigerant communication pipe into the corresponding indoor unit. The control unit reduces the opening degree of the second motor-operated valve in the first control. Thus, in the first control, the opening degree of the second motor-operated valve is adjusted, and the increase in the pressure of the refrigerant flowing into the operation unit is accurately and easily suppressed. Therefore, cost control can be achieved while suppressing, with high accuracy, an increase in noise in the operation unit associated with the gas-liquid two-phase conveyance.

The "second motor-operated valve" herein is an "electronic expansion valve that reduces the pressure of the refrigerant flowing from the refrigerant communication pipe into the corresponding indoor unit", and the location and number of the "second motor-operated valves" are not particularly limited as long as the increase in the pressure of the refrigerant flowing into the operation unit can be suppressed by adjusting the opening degree in the first control.

An air conditioning system according to a seventh aspect is the air conditioning system according to any one of the first to sixth aspects, further comprising an outdoor heat exchanger. The outdoor heat exchanger is disposed in the outdoor unit. The outdoor heat exchanger functions as a condenser or a radiator for the refrigerant. The electric valve is a third electric valve. The third motor-operated valve is disposed between the outdoor heat exchanger and the refrigerant communication pipe. The control unit reduces the opening degree of the third motor-operated valve in the first control.

Thus, in the first control, the opening degree of the third motor-operated valve is adjusted, and the increase in the pressure of the refrigerant flowing into the operation unit is accurately and easily suppressed. Therefore, cost control can be achieved while suppressing, with high accuracy, an increase in noise in the operation unit associated with the gas-liquid two-phase conveyance.

The "third motor-operated valve" herein is an "electronic expansion valve" disposed between the outdoor heat exchanger and the refrigerant communication pipe, and the location and number of the "third motor-operated valves" are not particularly limited as long as the increase in pressure of the refrigerant flowing into the operation unit can be suppressed by adjusting the opening degree in the first control.

Drawings

Fig. 1 is a schematic structural view of an air conditioning system according to an embodiment of the present disclosure;

fig. 2 is a schematic diagram showing an example of a refrigeration cycle in the forward cycle operation (normal control);

FIG. 3 is a block diagram schematically illustrating a controller and portions connected to the controller;

FIG. 4 is a flowchart showing an example of a process flow of the controller;

fig. 5 is a schematic diagram showing an example of a refrigeration cycle in a case where the feed-forward control is not executed when the operating capacity fluctuates;

fig. 6 is a schematic diagram showing an example of a refrigeration cycle in a case where feed-forward control is executed when the operating capacity fluctuates;

fig. 7 is a flowchart showing an example of the processing flow of the controller when calculating the valve opening degree of the electrically operated valve to be controlled in real time in the feedforward control.

Detailed Description

The following describes an air conditioning system 100 according to an embodiment of the present disclosure. The following embodiments are specific examples, and are not intended to limit the technical scope, and may be appropriately modified within the scope not departing from the gist thereof. In the following description, the "operation stop state" includes not only a state in which the operation is stopped due to an input of a command instructing the operation stop or a power supply interruption, but also a state in which the operation is suspended due to a thermal shutdown or the like.

(1) Overview of air conditioning system 100

Fig. 1 is a schematic configuration diagram of an air conditioning system 100. The air conditioning system 100 is installed in a building, a factory, or the like, and performs air conditioning of a target space. The air conditioning system 100 performs cooling, heating, and the like of the target space by performing a refrigeration cycle in the refrigerant circuit RC.

The air conditioning system 100 mainly includes an outdoor unit 10, a plurality of (4 or more in this case) indoor units 40(40a, 40b, 40c, and 40d …), a liquid-side communication pipe LC and a gas-side communication pipe GC that connect the outdoor unit 10 and the indoor units 40, and a controller 70 that controls the operation of the air conditioning system 100.

In the air conditioning system 100, the outdoor unit 10 and each indoor unit 40 are connected by a liquid-side communication pipe LC and a gas-side communication pipe GC to constitute a refrigerant circuit RC. In the air conditioning system 100, a vapor compression refrigeration cycle is performed, in which the refrigerant sealed in the refrigerant circuit RC is compressed, cooled or condensed, decompressed, heated or evaporated, and then compressed again. For example, R32 refrigerant is sealed in the refrigerant circuit RC.

In the air conditioning system 100, the liquid-side communication pipe LC extending between the outdoor unit 10 and the indoor unit 40 performs two-phase gas-liquid conveyance in which the refrigerant is conveyed in a two-phase gas-liquid state. More specifically, the air conditioning system 100 is configured to perform gas-liquid two-phase conveyance in the liquid-side communication pipe LC to achieve refrigerant saving, because the refrigerant conveyed in the liquid-side communication pipe LC extending between the outdoor unit 10 and the indoor unit 40 can be operated with a small refrigerant filling amount while suppressing a decrease in capacity when conveyed in a gas-liquid two-phase state, as compared to the case of conveyance in a liquid state.

The heat load here is a heat load to be handled in the operating indoor unit 40 (operating unit), and is calculated based on any one or all of a set temperature set in the operating unit, a temperature in a target space where the operating unit is installed, a refrigerant circulation amount, a rotation speed of the indoor fan 45, a rotation speed of the compressor 11, a capacity of the outdoor heat exchanger 14, a capacity of the indoor heat exchanger 42, and the like, for example.

(1-1) outdoor Unit 10

The outdoor unit 10 is installed outside a building such as a roof and a balcony, or outside a room (outside a target space) such as the ground. The outdoor unit 10 is connected to the plurality of indoor units 40 via the liquid-side communication pipe LC and the gas-side communication pipe GC, and constitutes a part of the refrigerant circuit RC.

The outdoor unit 10 mainly includes a plurality of refrigerant pipes (first pipe P1 to twelfth pipe P12), a compressor 11, an accumulator 12, a four-way switching valve 13, an outdoor heat exchanger 14, a subcooler 15, an outdoor first control valve 16, an outdoor second control valve 17, an outdoor third control valve 18, a liquid-side shutoff valve 19, and a gas-side shutoff valve 20.

The first pipe P1 connects the gas-side shutoff valve 20 and the first port of the four-way switching valve 13. The second pipe P2 connects the inlet port of the accumulator 12 and the second port of the four-way switching valve 13. The third pipe P3 connects the outlet port of the accumulator 12 and the suction port of the compressor 11. The fourth pipe P4 connects the discharge port of the compressor 11 and the third port of the four-way switching valve 13. The fifth pipe P5 connects the fourth port of the four-way switching valve 13 and the gas side inlet/outlet of the outdoor heat exchanger 14. The sixth pipe P6 connects the liquid side inlet/outlet of the outdoor heat exchanger 14 and one end of the outdoor first control valve 16. The seventh pipe P7 connects the other end of the outdoor first control valve 16 and one end of the main flow path 151 of the subcooler 15. The eighth pipe P8 connects the other end of the main flow path 151 of the subcooler 15 and one end of the outdoor second control valve 17. The ninth pipe P9 connects the other end of the outdoor second control valve 17 and one end of the liquid-side shutoff valve 19. The tenth pipe P10 connects a portion between both ends of the sixth pipe P6 and one end of the outdoor third control valve 18. The eleventh pipe P11 connects the other end of the outdoor third control valve 18 and one end of the sub-flow path 152 of the subcooler 15. The twelfth pipe P12 connects the portion between the other end of the sub-flow path 152 of the subcooler 15 and the both ends of the first pipe P1. These refrigerant pipes (P1-P12) may be actually constituted by a single pipe, or may be constituted by connecting a plurality of pipes via joints or the like.

The compressor 11 is a device that compresses a low-pressure refrigerant in a refrigeration cycle to a high pressure. In the present embodiment, the compressor 11 has a closed structure in which a positive displacement compression element such as a rotary type or a scroll type is rotationally driven by a compressor motor (not shown). Here, the compressor motor can control the operating frequency by the inverter, thereby enabling the capacity control of the compressor 11.

The accumulator 12 is a container for suppressing excessive suction of the liquid refrigerant into the compressor 11. The accumulator 12 has a predetermined volume according to the amount of refrigerant filled in the refrigerant circuit RC.

The four-way switching valve 13 is a flow path switching valve for switching the flow of the refrigerant in the refrigerant circuit RC. The four-way switching valve 13 can switch the forward circulation state and the reverse circulation state. In the forward circulation state, the four-way switching valve 13 communicates the first port (first pipe P1) with the second port (second pipe P2), and communicates the third port (fourth pipe P4) with the fourth port (fifth pipe P5) (see the solid line of the four-way switching valve 13 in fig. 1). In the reverse cycle state, the four-way switching valve 13 communicates the first port (first line P1) with the third port (fourth line P4), and communicates the second port (second line P2) with the fourth port (fifth line P5) (see the broken line of the four-way switching valve 13 in fig. 1).

The outdoor heat exchanger 14 is a heat exchanger functioning as a refrigerant condenser (or radiator) or an evaporator (or heater). The outdoor heat exchanger 14 functions as a condenser for the refrigerant during the forward circulation operation (operation in which the four-way switching valve 13 is in the forward circulation state). The outdoor heat exchanger 14 functions as an evaporator of the refrigerant during the reverse cycle operation (operation in which the four-way switching valve 13 is in the reverse cycle state). The outdoor heat exchanger 14 includes a plurality of heat transfer tubes and heat transfer fins (not shown). The outdoor heat exchanger 14 is configured to exchange heat between the refrigerant in the heat transfer tubes and air (outdoor air flow described later) passing around the heat transfer tubes or the heat transfer fins.

The subcooler 15 is a heat exchanger that sets the refrigerant flowing in to a subcooled liquid refrigerant. The subcooler 15 is, for example, a double-tube heat exchanger, and the subcooler 15 includes a main flow path 151 and a sub flow path 152. The subcooler 15 is configured to exchange heat between the refrigerant flowing through the main flow passage 151 and the sub-flow passage 152.

The outdoor first control valve 16 is an electronic expansion valve whose opening degree can be controlled, and reduces the pressure of the refrigerant flowing in or adjusts the flow rate of the refrigerant according to the opening degree. The outdoor first control valve 16 is disposed between the outdoor heat exchanger 14 and the subcooler 15 (main flow path 151). In other words, the outdoor first control valve 16 may be disposed in the outdoor heat exchanger 14 and the liquid-side communication pipe LC.

The outdoor second control valve 17 (corresponding to the "first motor-operated valve" in the claims) is an electronic expansion valve whose opening degree can be controlled, and reduces the pressure of the refrigerant flowing in or adjusts the flow rate of the refrigerant according to the opening degree. The outdoor second control valve 17 is disposed between the subcooler 15 (main channel 151) and the liquid-side shutoff valve 19. By controlling the opening degree of the outdoor second control valve 17, the refrigerant sent from the outdoor unit 10 to the liquid side communication pipe LC can be decompressed to be in a gas-liquid two-phase state.

The outdoor third control valve 18 is an electronic expansion valve whose opening degree is controllable, and reduces the pressure of the refrigerant flowing in or adjusts the flow rate of the refrigerant according to the opening degree. The outdoor third control valve 18 is disposed between the outdoor heat exchanger 14 and the subcooler 15 (sub-flow path 152).

The liquid-side shutoff valve 19 is a manual valve disposed at a connection portion between the ninth pipe P9 and the liquid-side communication pipe LC. One end of the liquid-side shutoff valve 19 is connected to the ninth pipe P9, and the other end is connected to the liquid-side communication pipe LC.

The gas-side shutoff valve 20 is a manual valve disposed at a connection portion between the first pipe P1 and the gas-side communication pipe GC. The gas-side shutoff valve 20 has one end connected to the first pipe P1 and the other end connected to the gas-side communication pipe GC.

In addition, the outdoor unit 10 has an outdoor fan 25 that generates an outdoor air flow passing through the outdoor heat exchanger 14. The outdoor fan 25 is a blower that supplies outdoor air flow, which is a cooling source or a heating source of the refrigerant flowing through the outdoor heat exchanger 14, to the outdoor heat exchanger 14. The outdoor fan 25 includes an outdoor fan motor (not shown) as a drive source, and is appropriately controlled to start/stop and rotate according to the situation.

In addition, in the outdoor unit 10, a plurality of outdoor side sensors 26 (see fig. 3) for detecting the state (mainly, pressure or temperature) of the refrigerant in the refrigerant circuit RC are arranged. The outdoor sensor 26 is a temperature sensor such as a pressure sensor, a thermistor, or a thermocouple. The outdoor side sensor 26 includes, for example, a suction pressure sensor that detects a suction pressure LP that is a pressure of the refrigerant on a suction side of the compressor 11, a discharge pressure sensor that detects a discharge pressure HP that is a pressure of the refrigerant on a discharge side of the compressor 11, a refrigerant temperature sensor that detects a temperature (e.g., a degree of supercooling SC) of the refrigerant in the outdoor heat exchanger 14, an outside air temperature sensor that detects an outside air temperature, and the like.

The outdoor unit 10 further includes an outdoor unit control unit 30 that controls the operation and state of each device included in the outdoor unit 10. The outdoor unit control section 30 includes a microcomputer having a CPU, a memory, or the like. The outdoor unit controller 30 is electrically connected to the respective devices (11, 13, 16, 17, 18, 25, etc.) included in the outdoor unit 10 or the outdoor sensor 26, and inputs and outputs signals to and from each other. The outdoor unit control unit 30 transmits and receives control signals and the like to and from the indoor unit control units 48 (described later) of the indoor units 40 and the remote controller 60 (see fig. 3) individually via communication lines (not shown).

(1-2) indoor Unit 40

Each indoor unit 40 is connected to the outdoor unit 10 via a liquid-side communication pipe LC and a gas-side communication pipe GC. Each indoor unit 40 is arranged in parallel or in series with the other indoor units 40 with respect to the outdoor unit 10. For example, in fig. 1, the indoor unit 40a and the indoor unit 40b are arranged in series, and the

indoor units

40c and 40d are arranged in parallel.

Each indoor unit 40 is disposed in the target space and constitutes a part of the refrigerant circuit RC. Each indoor unit 40 mainly includes a plurality of refrigerant pipes (thirteenth pipe P13 and fourteenth pipe P14), an indoor expansion valve 41, and an indoor heat exchanger 42.

The thirteenth pipe P13 connects the liquid side communication pipe LC and the liquid side refrigerant inlet and outlet of the indoor heat exchanger 42. The fourteenth pipe P14 connects the gas side refrigerant inlet/outlet of the indoor heat exchanger 42 and the gas side communication pipe GC. The refrigerant pipes (P13, P14) may be actually formed by a single pipe, or may be formed by connecting a plurality of pipes via joints or the like.

The indoor expansion valve 41 is an electronic expansion valve whose opening degree can be controlled, and reduces the pressure of the refrigerant flowing thereinto or adjusts the flow rate thereof according to the opening degree. The indoor expansion valve 41 is disposed in the thirteenth pipe P13 and between the liquid side communication pipe LC and the indoor heat exchanger 42. In the forward cycle operation, the indoor expansion valve 41 decompresses the refrigerant flowing into the indoor unit 40 from the liquid side communication pipe LC.

The indoor heat exchanger 42 is a heat exchanger functioning as a refrigerant evaporator (or a heater) or a condenser (or a radiator). The indoor heat exchanger 42 functions as an evaporator of the refrigerant during the forward cycle operation. The indoor heat exchanger 42 functions as a condenser of the refrigerant during the reverse cycle operation. The indoor heat exchanger 42 includes a plurality of heat transfer tubes and heat transfer fins (not shown). The indoor heat exchanger 42 is configured to exchange heat between the refrigerant in the heat transfer tubes and air (indoor air flow described later) passing around the heat transfer tubes or the heat transfer fins.

The indoor unit 40 includes an indoor fan 45, and the indoor fan 45 sucks air in the target space, passes the air through the indoor heat exchanger 42, exchanges heat with the refrigerant, and then sends the air into the target space again. The indoor fan 45 is disposed in the target space. The indoor fan 45 includes an indoor fan motor (not shown) as a driving source. The indoor fan 45 generates an indoor air flow as a heating source or a cooling source of the refrigerant flowing through the indoor heat exchanger 42 when driven.

In addition, an indoor sensor 46 (see fig. 3) for detecting a state (mainly, pressure or temperature) of the refrigerant in the refrigerant circuit RC is disposed in the indoor unit 40. The indoor side sensor 46 is a temperature sensor such as a pressure sensor, a thermistor, or a thermocouple. The indoor side sensor 46 includes, for example, a temperature sensor that detects the temperature (e.g., the degree of superheat) of the refrigerant in the indoor heat exchanger 42, a pressure sensor that detects the pressure of the refrigerant, and the like.

The indoor unit 40 includes an indoor unit control unit 48 that controls the operation and state of each device included in the indoor unit 40. The indoor unit control unit 48 includes a microcomputer including a CPU, a memory, and the like. The indoor unit control unit 48 is electrically connected to the devices (41, 45) included in the indoor unit 40 or the indoor sensor 46, and inputs and outputs signals to and from each other. The indoor-unit control unit 48 is connected to the outdoor-unit control unit 30 or a remote controller 60 (see fig. 3) via a communication line (not shown), and transmits and receives control signals and the like.

(1-3) liquid-side communication pipe LC and gas-side communication pipe GC

The liquid-side communication pipe LC and the gas-side communication pipe GC are communication pipes for connecting the outdoor unit 10 and the indoor units 40, and are constructed on site. The pipe length and pipe diameter of the liquid side communication pipe LC and the gas side communication pipe GC are appropriately selected in accordance with the design specification and installation environment. The liquid-side communication pipe LC and the gas-side communication pipe GC may be actually constituted by a single pipe, or may be constituted by connecting a plurality of pipes via a joint or the like.

In the present embodiment, the liquid-side communication pipe LC branches into a plurality of branches (liquid-side communication pipes L1, L2 …). The gas-side communication pipe GC is branched into a plurality of branches (gas-side communication pipes G1, G2 …). In fig. 1, the indoor units 40a and 40b and the like are individually connected to the liquid side communication pipe L1 and the gas side communication pipe G1, and the

indoor units

40c and 40d and the like are individually connected to the liquid side communication pipe L2 and the gas side communication pipe G2.

(1-4) controller 70

The controller 70 (corresponding to the "detection unit" and the "control unit" in the claims) is a computer that controls the operation of the air conditioning system 100 by controlling the state of each device. In the present embodiment, the controller 70 is configured such that the outdoor unit control unit 30 and the indoor unit control unit 48 in each indoor unit 40 are connected via a communication line. Details of the controller 70 are described in "(3) details of the controller 70" described later.

(2) Flow of refrigerant in the refrigerant circuit RC

The flow of the refrigerant in the refrigerant circuit RC will be described below. The air conditioning system 100 mainly performs a forward cycle operation such as a cooling operation and a reverse cycle operation such as a heating operation. Here, the low pressure in the refrigeration cycle is the pressure of the refrigerant sucked by the compressor 11, and the high pressure in the refrigeration cycle is the pressure of the refrigerant discharged from the compressor 11. Further, the indoor expansion valve 41 of the indoor unit 40 in the operation stopped state (operation suspended state) is controlled to be in the closed state.

(2-1) flow of refrigerant during Forward cycle operation

Fig. 2 is a schematic diagram showing an example of the refrigeration cycle during the forward cycle operation (during normal control). In the forward circulation operation, the four-way switching valve 13 is controlled to be in the forward circulation state, and the refrigerant filled in the refrigerant circuit RC circulates mainly in the order of the compressor 11, the outdoor heat exchanger 14, the outdoor first control valve 16, the subcooler 15 (the main flow path 151), the outdoor second control valve 17, the indoor expansion valve 41 and the indoor heat exchanger 42 of the operating indoor unit 40 (the operating unit), and the compressor 11. In the forward cycle operation, a part of the refrigerant flowing through the sixth pipe P6 is branched to the ninth pipe P9, passes through the outdoor third control valve 18 and the subcooler 15 (sub-passage 152), and then returns to the compressor 11.

Specifically, when the forward cycle operation is started, the refrigerant is sucked into the compressor 11, compressed to a high pressure in the refrigeration cycle, and discharged from the outdoor unit 10 (see a-b of fig. 2). In the compressor 11, capacity control is performed in accordance with a heat load required in the operation unit. Specifically, a target value of the suction pressure LP (see a in fig. 2) is set in accordance with the heat load required in the indoor unit 40, and the operating frequency of the compressor 11 is controlled so that the suction pressure LP reaches the target value. The gas refrigerant discharged from the compressor 11 flows into the gas-side inlet/outlet of the outdoor heat exchanger 14.

The gas refrigerant flowing into the outdoor heat exchanger 14 exchanges heat with the outdoor air flow sent by the outdoor fan 25 in the outdoor heat exchanger 14, and dissipates heat and condenses (see b-d in fig. 2). At this time, the refrigerant becomes a supercooled liquid refrigerant (see c-d of fig. 2) with a degree of supercooling SC. The refrigerant flowing out of the liquid side inlet/outlet of the outdoor heat exchanger 14 branches while flowing through the sixth pipe P6.

One of the refrigerants branched while passing through the sixth pipe P6 flows into the main flow path 151 of the subcooler 15 through the outdoor first control valve 16. The refrigerant flowing into the main flow passage 151 of the subcooler 15 exchanges heat with the refrigerant flowing through the sub flow passage 152 to be cooled, and is further brought into a state with a degree of subcooling (see d-e of fig. 2).

The liquid refrigerant flowing out of the main flow passage 151 of the subcooler 15 is decompressed or flow-regulated according to the opening degree of the outdoor second control valve 17, and becomes a gas-liquid two-phase state, and becomes an intermediate-pressure refrigerant (see e-f in fig. 2) having a pressure lower than the high-pressure refrigerant and a pressure higher than the low-pressure refrigerant. Thus, during the forward cycle operation, the refrigerant in the gas-liquid two-phase state is sent to the liquid-side communication pipe LC, and the refrigerant sent from the outdoor unit 10 side to the indoor unit 40 side is sent in the gas-liquid two-phase state. In this connection, as compared with the case where the refrigerant flowing through the liquid-side communication pipe LC is liquid-conveyed in a liquid state, the liquid-side communication pipe LC is not filled with the liquid refrigerant, and the amount of the refrigerant existing in the liquid-side communication pipe LC can be reduced accordingly.

In the present embodiment, the opening degree of the outdoor second control valve 17 is appropriately controlled so that the degree of subcooling SC (see c-d in fig. 2) of the refrigerant on the liquid side of the outdoor heat exchanger 14 becomes the target degree of subcooling. Specifically, when the supercooling degree SC is larger than the target supercooling degree, the opening degree of the outdoor second control valve 17 is increased, and when the supercooling degree SC is smaller than the target supercooling degree, the opening degree of the outdoor second control valve 17 is decreased.

When the gas-liquid two-phase refrigerant flowing out of the outdoor unit 10 passes through the liquid-side communication pipe LC, the pressure decreases due to pressure loss (see f-g in fig. 2). Then, the refrigerant flows into the operation unit.

The other refrigerant branched while passing through the sixth pipe P6 flows into the outdoor third control valve 18, is subjected to pressure reduction or flow rate adjustment according to the opening degree of the outdoor third control valve 18, and then flows into the sub-flow path 152 of the subcooler 15. The refrigerant flowing into the sub-flow passage 152 of the subcooler 15 exchanges heat with the refrigerant flowing through the main flow passage 151, and then joins the refrigerant flowing through the first pipe P1 via the twelfth pipe P12.

The refrigerant flowing into the operation unit flows into the indoor expansion valve 41, is decompressed to a low pressure in the refrigeration cycle (see g-h in fig. 2) according to the opening degree of the indoor expansion valve 41, and then flows into the indoor heat exchanger 42.

Further, as described above, the gas-liquid two-phase conveyance is performed in the refrigerant circuit RC. Therefore, the amount of pressure reduction in the indoor expansion valve 41 (see g-h in fig. 2) is smaller than the amount of pressure reduction at the time of liquid transport (corresponding to the pressure obtained by subtracting the amount of pressure loss in the liquid-side communication pipe LC from the pressure difference between e-h in fig. 2). In this connection, the opening degree of the indoor expansion valve 41 is larger than that in the case of liquid conveyance.

The refrigerant flowing into the indoor heat exchanger 42 exchanges heat with the indoor air flow sent by the indoor fan 45, evaporates, and turns into a gas refrigerant (see h-a in fig. 2). The gas refrigerant flowing out of the indoor heat exchanger 42 flows out of the indoor unit 40.

The refrigerant flowing out of the indoor unit 40 flows into the outdoor unit 10 through the gas-side communication pipe GC. The refrigerant flowing into the outdoor unit 10 flows through the first pipe P1, and flows into the accumulator 12 through the four-way switching valve 13 and the second pipe P2. The refrigerant flowing into the accumulator 12 is temporarily stored and then sucked into the compressor 11 again.

(2-2) flow of refrigerant in reverse cycle operation

In the reverse cycle operation, the four-way switching valve 13 is controlled to be in the reverse cycle state, and the refrigerant charged in the refrigerant circuit RC circulates mainly in the order of the compressor 11, the indoor heat exchanger 42 and the indoor expansion valve 41 of the operation unit, the outdoor second control valve 17, the subcooler 15, the outdoor first control valve 16, the outdoor heat exchanger 14, and the compressor 11.

Specifically, when the reverse cycle operation is started, the refrigerant is sucked into the compressor 11, compressed to a high pressure, and then discharged. In the compressor 11, capacity control is performed in accordance with a heat load required in the operation unit. The gas refrigerant discharged from the compressor 11 flows out of the outdoor unit 10 through the fourth pipe P4 and the first pipe P1, and flows into the operation unit through the gas-side communication pipe GC.

The refrigerant flowing into the indoor unit 40 flows into the indoor heat exchanger 42, exchanges heat with the indoor air flow sent by the indoor fan 45, and condenses. The refrigerant flowing out of the indoor heat exchanger 42 flows into the indoor expansion valve 41, and is reduced in pressure to a low pressure in the refrigeration cycle by the opening degree of the indoor expansion valve 41. After that, the refrigerant flows out of the indoor unit 40.

The refrigerant flowing out of the indoor unit 40 flows into the operation unit through the liquid-side communication pipe LC. The refrigerant flowing into the outdoor unit 10 passes through the ninth pipe P9, the outdoor second control valve 17, the eighth pipe P8, the subcooler 15 (main passage 151), the seventh pipe P7, the outdoor first control valve 16, and the sixth pipe P6, and flows into the liquid-side inlet of the outdoor heat exchanger 14.

The refrigerant flowing into the outdoor heat exchanger 14 exchanges heat with the outdoor air flow sent by the outdoor fan 25 in the outdoor heat exchanger 14, and evaporates. Thereafter, the refrigerant flows out from the gas side inlet/outlet of the outdoor heat exchanger 14, passes through the fifth pipe P5, the four-way switching valve 13, and the second pipe P2, and flows into the accumulator 12. The refrigerant flowing into the accumulator 12 is temporarily stored and then sucked into the compressor 11 again.

(3) Details of the controller 70

In the air conditioning system 100, the outdoor unit control unit 30 and the indoor unit control unit 48 are connected by a communication line to constitute a controller 70. Fig. 3 is a block diagram schematically showing the controller 70 and parts connected to the controller 70.

The controller 70 has a plurality of control modes, and controls the operation of each device according to the control mode being transitioned. In the present embodiment, the controller 70 has, as control modes, a forward cycle operation mode in which the operation is transitioned during a forward cycle operation such as a cooling operation and a reverse cycle operation mode in which the operation is transitioned during a reverse cycle operation such as a heating operation.

The controller 70 is electrically connected to devices included in the air conditioning system 100 (specifically, the compressor 11, the outdoor first control valve 16, the outdoor second control valve 17, the outdoor third control valve 18, the outdoor fan 25, the outdoor sensor 26, the indoor expansion valve 41, the indoor fan 45, the indoor sensor 46, and the remote controllers 60 included in the indoor units 40, respectively).

The controller 70 mainly includes a storage section 71, an input control section 72, a mode control section 73, an operating capacity fluctuation detection section 74, an equipment control section 75, a drive signal output section 76, and a display control section 77. Each of these functional units in the controller 70 is realized by a CPU, a memory, and various electric and electronic components included in the outdoor unit control unit 30 and/or the indoor unit control unit 48 functioning integrally.

(3-1) storage section 71

The storage section 71 is configured by, for example, a ROM, a RAM, a flash memory, and the like, and includes a volatile storage area and a nonvolatile storage area. The storage section 71 includes a program storage area M1 storing control programs defining processing in each section of the controller 70.

The storage unit 71 includes a detection value storage area M2 for storing detection values of various sensors. For example, the detection values (the suction pressure LP, the discharge pressure HP, the refrigerant temperature in the outdoor heat exchanger 14, the refrigerant temperature in the indoor heat exchanger 42, and the like) of the outdoor sensor 26 and the indoor sensor 46 are stored in the detection value storage region M2.

The storage unit 71 includes an equipment information storage area M3 for storing information (equipment information) specifying the characteristics and states of each piece of equipment included in the air conditioning system 100. The device information stored in the device information storage area M3 includes, for example, the rotation speed (frequency) of the compressor 11, the rotation speed (air volume) of the outdoor fan 25, the rotation speed (air volume) of each indoor fan 45, the opening degree (pulse) of each control valve (the outdoor first control valve 16, the outdoor second control valve 17, the outdoor third control valve 18, and each indoor expansion valve 41), and the state of the four-way switching valve 13. When the operating state of the device changes, the device information stored in the device information storage area M3 is appropriately updated. The device information also includes Cv values (coefficients representing flow rate characteristics and values having a correlation with the opening degree) of the respective electrically operated valves (16, 17, 18, 41). In addition, the device information includes capability information specifying the air conditioning capability of each indoor unit 40. The "air conditioning capacity" is a value (kW) indicating a heat load handling capacity of the indoor unit during operation, such as a cooling capacity, and is converted into horsepower. The air conditioning capacity of the indoor unit 40 is mainly determined based on the capacity of the indoor heat exchanger 42 and the like.

The storage unit 71 includes a command storage area M4 for storing commands to be input to the remote controllers 60.

The storage unit 71 includes a normal control storage area M5 storing a table (normal control table) defining the control contents in normal control (described later). Typically the control table is updated by an administrator as appropriate.

The storage unit 71 includes an FF control condition storage area M6 storing a table (FF control condition table) defining FF control conditions (described later) that trigger execution of feedforward control (described later). The FF control condition table (predetermined information) is set according to design specifications and installation environments, and defines FF control conditions according to the state of the equipment, the detection values of the

sensors

26 and 46, input commands, and the like, for example, according to the situation. The FF control condition table is updated by the administrator as appropriate.

The storage unit 71 includes an FF control storage area M7 storing a table (FF control table) defining the control content in the feedforward control. The FF control table is updated by the administrator as appropriate.

The storage unit 71 is provided with a plurality of flags having a predetermined number of bits. For example, the storage unit 71 is provided with a control mode determination flag M8 that can determine the control mode in which the controller 70 is transitioning. The control mode discrimination flag M8 contains the number of bits corresponding to the number of control modes, and establishes bits corresponding to the control mode being transitioned.

Further, the storage unit 71 is provided with an FF control flag M9 for determining whether or not the FF control condition is satisfied. The FF control flag M9 is set when the operating capacity variation detecting unit 74 determines that the FF control condition is satisfied. When the feed-forward control is completed, the FF control flag M9 is cleared by the apparatus control unit 75. The FF control flag M9 includes a predetermined number of bits, and is set up to have different bits according to the degree of variation in the operating capacity. That is, the FF control flag M9 is configured to be able to determine not only that the FF control condition is satisfied (i.e., that the operating capacity greatly fluctuates), but also the degree of fluctuation of the operating capacity.

(3-2) input control section 72

The input control unit 72 is a functional unit that realizes a function as an interface for receiving signals output from each device connected to the controller 70. For example, the input control unit 72 receives signals output from the sensors (26, 46) or the remote controller 60, stores the signals in corresponding storage areas of the storage unit 71, or sets a predetermined flag.

(3-3) mode control section 73

The mode control unit 73 is a functional unit that switches the control mode. When a command to perform the forward cycle operation is input, the mode control unit 73 switches the control mode to the forward cycle operation mode. When a command to perform the reverse cycle operation is input, the mode control unit 73 switches the control mode to the reverse cycle operation mode. The mode control unit 73 establishes the control mode discrimination flag M8 according to the control mode being transited.

(3-4) operating Capacity variation detecting section 74

The operating capacity variation detecting unit 74 (corresponding to the "detecting unit" in the claims) is a functional unit that detects a large variation in the operating capacity of the air conditioning system 100. Specifically, when the FF control condition is satisfied based on the FF control condition table, the operating capacity variation detecting unit 74 determines that the operating capacity of the air conditioning system 100 has significantly varied, and establishes the FF control flag M9. The FF control condition is defined in advance in the FF control condition table in accordance with design specifications and installation environments, as a condition that is assumed to have a large variation in operating capacity.

In the present embodiment, the FF control condition is satisfied when the number of operating indoor units 40 (operating units) varies beyond a predetermined ratio during the forward cycle operation. For example, the FF control condition is satisfied when the number of operating units decreases by a predetermined number (e.g., 2) or more (i.e., when the predetermined number or more of operating units are in the operation-stopped state) during a predetermined period Pt (e.g., 30 seconds). Further, for example, the FF control condition is satisfied when the number of operating units increases by a predetermined number (for example, 2) or more (that is, when the predetermined number or more of the indoor units 40 in the operation stop state are in the operating state) during a predetermined period Pt (for example, 30 seconds). The predetermined period Pt is defined in accordance with the design specification of the system, the installation environment, the usage state (the number of operating units, the number of stopping units, the degree of fluctuation in operating capacity, the magnitude of thermal load, or the device information) and the like.

The operating capacity fluctuation detection unit 74 determines whether or not the FF control condition is satisfied based on the FF control condition table stored in the FF control condition storage area M6, based on various information (for example, the detection values of the sensors 26 and/or 46 stored in the detection value storage area M2, the device information stored in the device information storage area M3, and/or the input command stored in the command storage area M4) stored in the storage unit 71. The operating capacity variation detecting unit 74 is configured to be able to measure time.

When the FF control condition is satisfied, the operating capacity variation detecting unit 74 specifies the degree of variation in the operating capacity, and sets different bits of the FF control flag M9 according to the degree of variation.

(3-5) device control section 75

The equipment control unit 75 (corresponding to the "control unit" in the claims) controls the operation of each equipment (for example, 11, 13, 16, 17, 18, 25, 41, 45, etc.) included in the air conditioning system 100 according to the situation, in accordance with the control program. The plant control unit 75 determines the control mode in transition by referring to the control mode determination flag M8, and controls the operation of each plant based on the control mode and the detection value of each sensor 26 and/or 46.

The device control section 75 executes various controls according to circumstances. For example, the device control unit 75 stops the indoor fan 45 and controls the indoor expansion valve 41 to be in the closed state to be in the operation stop state for the operation means to which the instruction for instructing the operation stop is input and the operation means for which the indoor temperature reaches the set temperature.

For example, the device control unit 75 executes the following normal control and feed control depending on the situation. The device control unit 75 is configured to be able to measure time.

General control

During operation, the device control unit 75 executes normal control in accordance with an input command, a thermal load, and the like, based on the normal control table stored in the normal control storage area M5, in a normal state (when the FF control condition is not satisfied, that is, when the FF control flag M9 is not established).

In the forward circulation operation mode, the device control unit 75 controls the rotation speed of the compressor 11, the rotation speeds of the outdoor fan 25 and the indoor fan 45, the opening degree of the outdoor second control valve 17, the opening degree of the outdoor third control valve 18, the opening degree of the indoor expansion valve 41, and the like in real time based on the set temperature, the detection values of the sensors, and the like, so as to perform forward circulation operation in which the suction pressure LP, the discharge pressure HP, the degree of supercooling SC, the degree of superheat, and the like become target values. During the forward cycle operation, the equipment control unit 75 controls the four-way switching valve 13 to the forward cycle state, and causes the outdoor heat exchanger 14 to function as a condenser (or radiator) for the refrigerant, while causing the indoor heat exchanger 42 of the operating unit to function as an evaporator (or radiator) for the refrigerant.

In the reverse cycle operation mode, the device control unit 75 controls the rotation speed of the compressor 11, the rotation speeds of the outdoor fan 25 and the indoor fan 45, the opening degree of the outdoor first control valve 16, the opening degree of the indoor expansion valve 41, and the like in real time to perform the reverse cycle operation based on the set temperature, the detection values of the sensors, and the like. In the reverse cycle operation, the appliance control unit 75 controls the four-way switching valve 13 to the reverse cycle state, and causes the outdoor heat exchanger 14 to function as an evaporator (or heater) of the refrigerant, and causes the indoor heat exchanger 42 of the operating unit to function as a condenser (or heater) of the refrigerant.

Feedforward control

In the forward circulation operation, when the FF control condition is satisfied (i.e., when the FF control flag M9 is established), the device control unit 75 performs the feed-forward control (corresponding to the "first control" described in claims) based on the FF control table stored in the FF control storage region M7. The feedforward control is a control for suppressing a significant increase in the inflow of refrigerant in the operation unit that is in the operation state from before the change in the operation capacity by adjusting the opening degree of a predetermined electrically operated valve included in the refrigerant circuit RC when the operation capacity greatly changes, and suppressing the generation of noise associated with this. The feed-forward control is an interrupt control executed in preference to the normal control when the FF control condition is satisfied when the normal control is performed during the forward circulation operation.

In the feedforward control, the equipment control unit 75 reduces the opening degree of a predetermined motor-operated valve (e.g., 16, 17, 41, etc.) included in the refrigerant circuit RC so as to reduce the pressure or flow rate of the refrigerant flowing into the operating unit that is in the operating state from before the operating capacity is changed. This makes it possible to suppress a temporary increase in the inflow of refrigerant into the operation unit even when the operation capacity greatly fluctuates, particularly in the case of gas-liquid two-phase conveyance (that is, in the case where the opening degree of the indoor expansion valve 41 in the operation unit is larger than that in the case of liquid conveyance). In other words, in the feedforward control, the decompression ratio of the motor-operated valve to be controlled is controlled so that the refrigerant pressure at the inlet of the indoor expansion valve 41 in the operating unit that is maintained in the operating state from before the feedforward control is executed (i.e., before the operating capacity is changed) does not change significantly after the operating capacity is changed. In the present embodiment, in the feedforward control, the outdoor second control valve 17 is set as a control target, and the outdoor second control valve 17 is reduced to an opening degree that responds to the situation.

In the FF control table, the range of the decreased opening degree is defined individually according to the magnitude of the varied operation capacity. That is, in the FF control table, the adjusted decompression ratio and valve opening degree are defined for each case of the electrically operated valve to be subjected to the feedforward control.

After the execution of the feedforward control is started, when a predetermined FF control completion condition is satisfied, the apparatus control portion 75 completes the feedforward control. The FF control completion condition is defined in the FF control table, assuming that the risk of a significant increase in the inflow of refrigerant to the operation unit is eliminated by performing the feed-forward control when the variation in the operation capacity occurs. In the present embodiment, the FF control completion condition is satisfied by the elapse of a predetermined time t1 after the execution of the feedforward control. The predetermined time t1 is defined according to the situation based on the number of operating units, the number of stopping units, the degree of fluctuation in operating capacity, the magnitude of thermal load, or the device information. For example, the predetermined time t1 is set to 1 minute.

The details of the feedforward control are explained in "(5) the details of the feedforward control" described later.

(3-6) drive signal output section 76

The drive signal output unit 76 outputs a corresponding drive signal (drive voltage) to each device (11, 13, 16, 17, 18, 25, 41, 45, etc.) according to the control content of the device control unit 75. The drive signal output unit 76 includes a plurality of inverters (not shown), and outputs a drive signal from a corresponding inverter to a specific device (for example, the compressor 11, the outdoor fan 25, or each indoor fan 45).

(3-7) display control section 77

The display control unit 77 is a functional unit that controls the operation of the remote controller 60 as a display device. The display control unit 77 causes the remote controller 60 to output predetermined information so as to display information on the operation state and the status to the user. For example, the display control unit 77 causes the remote controller 60 to display various information such as the set temperature during the normal mode operation.

(4) Processing flow of the controller 70

An example of the processing flow of the controller 70 will be described below with reference to fig. 4. Fig. 4 is a flowchart showing an example of the processing flow of the controller 70. When the power is turned on, the controller 70 performs processing in the flow shown in steps S101 to S106 of fig. 4. The processing flow shown in fig. 4 is an example, and may be changed as appropriate. For example, the order of steps may be changed without contradiction, or a part of steps may be executed in parallel with other steps, or other steps may be newly added.

In step S101, if the operation means is present (i.e., YES), the controller 70 proceeds to step S103. In the case where there is NO operating unit (i.e., in the case of NO), the controller 70 proceeds to step S102.

In step S102, the controller 70 switches each device to a stopped state (or maintains the stopped state of each device). Thereafter, the process returns to step S101.

In step S103, if the FF control condition is not satisfied (i.e., if the operating capacity does not change significantly, in this case, if NO), the controller 70 proceeds to step S106. On the other hand, when the FF control condition is satisfied (that is, when the operating capacity greatly fluctuates, YES in this case), the controller 70 proceeds to step S104.

In step S104, the controller 70 executes feed-forward control. Specifically, in the feedforward control, the controller 70 determines the decompression ratio of the outdoor second control valve 17 in accordance with the situation based on the FF control table, the equipment information, and the like to suppress pressure fluctuation of the refrigerant flowing into the operation unit maintaining the operation state, and decreases the opening degree of the outdoor second control valve 17 in accordance with the decompression ratio. After that, the controller 70 proceeds to step S105.

In step S105, if the FF control completion condition is not satisfied (i.e., if it is not assumed that the risk of a significant increase in the flow of refrigerant into the operation unit is eliminated, in this case, NO), the controller 70 remains in step S105. On the other hand, when the FF control completion condition is satisfied (that is, when it is assumed that the risk of a significant increase in the inflow of the refrigerant to the operation unit is eliminated, YES in this case), the controller 70 proceeds to step S106.

In step S106, the controller 70 executes normal control. Specifically, the controller 70 performs the forward cycle operation or the reverse cycle operation by controlling the state of each device in real time based on an input command, a set temperature, and detection values of the sensors (26, 46). Thereafter, the process returns to step S101.

(5) Details of feed-forward control

As described above, in the air conditioning system 100, when the FF control condition is satisfied during operation, the feedforward control is executed by the controller 70 (the device control unit 75). This feedforward control is control for suppressing noise increase and increase in sound of refrigerant passing through the operation unit in association with gas-liquid two-phase conveyance.

That is, in order to achieve refrigerant saving, in relation to the refrigerant transported through the liquid-side refrigerant flow path extending between the outdoor unit and the indoor unit, when the gas-liquid two-phase transport is performed in which the refrigerant is transported in a gas-liquid two-phase state, the opening degree of the indoor expansion valve is generally larger than that in the case of the liquid transport. Therefore, if the operating state of a predetermined number or more of indoor units significantly fluctuates (i.e., the operating capacity significantly increases or decreases), the refrigerant flow rate significantly increases in the indoor units that remain in operation (forward cycle operation) until the operating capacity fluctuates. In particular, when a plurality of indoor units are simultaneously in an operation-suspended state, there is a high possibility that such a situation occurs. As a result of this occurrence, the sound of refrigerant passing through the operating indoor unit becomes louder, and noise may be generated.

In this regard, when the FF control condition is satisfied (that is, when the operating capacity is greatly increased or decreased), the feed-forward control is executed, whereby the predetermined motor-operated valve (here, the outdoor second control valve 17) reduces the opening degree (adjusts the decompression ratio) so as to absorb the fluctuation in the operating capacity, thereby reducing the pressure or flow rate of the refrigerant flowing through the liquid side communication pipe LC. As a result, the inflow of the refrigerant into the operation unit is suppressed from temporarily increasing with a large fluctuation in the operation capacity. In this connection, when the operating capacity greatly fluctuates, the occurrence of noise in the operating unit is suppressed.

Fig. 5 is a schematic diagram showing an example of a refrigeration cycle in a case where the feed-forward control is not executed when the operating capacity fluctuates. Fig. 6 is a schematic diagram showing an example of a refrigeration cycle in a case where the feed-forward control is executed when the operating capacity fluctuates.

As shown in fig. 5, when the operating capacity greatly fluctuates (that is, when the FF control condition is satisfied), if the feed-forward control is not executed, the pressure reduction amount in the outdoor second control valve 17 is temporarily reduced (see e-f' of fig. 5). In this connection, the amount of pressure reduction by the indoor expansion valve 41 in the operating unit that was in operation until the operating capacity varied is increased (see g' -h in fig. 5). Therefore, the pressure of the refrigerant flowing into the indoor expansion valve 41 of the operating unit temporarily increases, and noise is generated.

On the other hand, as shown in fig. 6, when the operating capacity greatly fluctuates (that is, when the FF control condition is satisfied), the opening degree of the outdoor second control valve 17 is decreased according to the degree of fluctuation of the operating capacity when the feedforward control is executed, whereby the decrease in the amount of pressure reduction in the outdoor second control valve 17 is suppressed as compared with the case where the feedforward control is not executed (fig. 6 shows a case where the amount of pressure reduction in the outdoor second control valve 17 is increased as compared with the case where the normal control is executed; see e-f ″ of fig. 6). In this connection, it is suppressed that the decompression amount of the indoor expansion valve 41 in the operating unit that was in the operating state from the time of the variation in the operating capacity becomes larger than in the case where the feedforward control is not executed (fig. 6 shows a case where the decompression amount of the indoor expansion valve 41 is about the same as in the case where the normal control is executed; see g-h of fig. 6). Therefore, the pressure of the refrigerant flowing into the indoor expansion valve 41 of the operating unit temporarily increases, and the occurrence of noise is suppressed.

For example, when the operating capacity greatly fluctuates, the degree of sound in the operating unit when the feedforward control is not performed is 38dB (32 dB in the case of liquid transfer), whereas the degree of sound in the operating unit when the feedforward control is not performed is reduced to 31 dB.

(6) Feature(s)

(6－1)

In the air conditioning system 100 of the above embodiment, when the operating capacity variation detecting unit 74 detects a change in the number of operating units, the controller 70 (the equipment control unit 75) executes feed-forward control in which the opening degree of the outdoor second control valve 17 is adjusted to suppress an increase in the pressure of the refrigerant flowing into the operating units. Thus, when the number of operating units of the indoor unit 40 is changed, the increase in the pressure of the refrigerant flowing into the operating units is suppressed by adjusting the opening degree of the predetermined electrically-operated valve (here, the outdoor second control valve 17). As a result, noise increase in the operation unit is suppressed.

(6－2)

In the air conditioning system 100 of the above embodiment, the refrigerant flowing from the outdoor unit 10 to the indoor unit 40 is sent in a gas-liquid two-phase state. Thus, when the operation capacity is greatly changed (due to a large change in the operation state of the plurality of indoor units 40) during gas-liquid two-phase conveyance in which the opening degree of the indoor expansion valve 41 is increased, the amount of pressure reduction in the indoor expansion valve 41 is also suppressed from temporarily increasing, as compared with the case of liquid conveyance. Therefore, the increase in noise in the operation unit associated with the gas-liquid two-phase conveyance is suppressed.

(6－3)

In the air conditioning system 100 according to the above-described embodiment, the controller 70 is configured to execute the feed-forward control when the operating capacity variation detecting unit 74 detects a decrease in the number of operating units. In this regard, when the plurality of indoor units 40 are simultaneously in the operation stop state, the rotation speed of the compressor 11 is adjusted, and the opening degree of the outdoor second control valve 17 and the like is adjusted in accordance with the change in the supercooling degree SC as time elapses. Before this state is reached, the amount of refrigerant flowing into the operation unit temporarily increases. That is, when the plurality of indoor units 40 are brought into the operation stop state at the same time, it is strongly assumed that the sound of refrigerant passing through the indoor units 40 during operation is increased to generate noise, and in the air conditioning system 100, when the operation capacity detection unit 74 detects a decrease in the number of operating units, the controller 70 performs the feedforward control, thereby suppressing this situation.

(6－4)

In the air conditioning system 100 of the above embodiment, the electrically operated valve whose opening degree is adjusted in the feedforward control is the outdoor second control valve 17 (first electrically operated valve) that reduces the pressure of the refrigerant flowing from the outdoor unit 10 to the indoor unit 40 in a gas-liquid two-phase state so that the refrigerant passes through the refrigerant communication pipe. In the feed-forward control, the opening degree of the outdoor second control valve 17 is adjusted so as to accurately and simply suppress an increase in the pressure of the refrigerant flowing into the operation unit. Therefore, cost control can be achieved while suppressing, with high accuracy, an increase in noise in the operation unit associated with the gas-liquid two-phase conveyance.

(7) Modification example

The above embodiment can be modified as appropriate as shown in the following modification examples. Each modification may be combined with other modifications to the extent that no contradiction occurs.

(7-1) modification 1

In the above embodiment, the controller 70 (the device controller 75) is configured to reduce the opening degree of the electrically-operated valve (the outdoor second control valve 17) to be controlled during operation based on the control table FF in which the decompression ratio of the electrically-operated valve (the valve opening degree is defined as the case may be) is defined according to the magnitude of the varying operation capacity during the feedforward control.

However, the present invention is not necessarily limited to this, and the controller 70 may determine the decompression ratio of the electrically operated valve to be controlled in real time based on predetermined information in the feedforward control, and may reduce the electrically operated valve to a valve opening corresponding to the decompression ratio. That is, the controller 70 may calculate the valve opening in real time in the feed-forward control instead of using the opening defined in the FF control table. An example of the case where the controller 70 calculates the valve opening of the electrically operated valve to be controlled in real time during the feedforward control will be described below.

For example, the controller 70 executes the processing in the flow shown in steps S201 to S207 shown in fig. 7. Fig. 7 is a flowchart showing an example of the processing flow of the controller 70 when calculating the valve opening degree of the electrically operated valve to be controlled in real time in the feedforward control. The processing flow shown in fig. 7 is an example, and may be changed as appropriate. For example, the order of steps may be changed without contradiction, or a part of steps may be executed in parallel with other steps, or other steps may be newly added.

In step S201, if the operation means is present (i.e., YES), the controller 70 proceeds to step S203. In the case where there is NO operating unit (i.e., in the case of NO), the controller 70 proceeds to step S202.

In step S202, the controller 70 switches each device to a stopped state (or maintains the stopped state of each device). After that, the process returns to step S201.

In step S203, the controller 70 executes normal control. Specifically, the controller 70 performs the forward cycle operation or the reverse cycle operation by controlling the state of each device in real time based on an input command, a set temperature, and detection values of the sensors (26, 46). After that, the process proceeds to step S204.

In step S204, the controller 70 predicts the outlet pressure of the outdoor second control valve 17 based on the refrigerant circulation amount, the valve opening degree (Cv value of the current opening degree) of the outdoor second control valve 17, the inlet density and the inlet pressure of the outdoor second control valve 17, and the like (see f in fig. 2). The refrigerant circulation amount is calculated based on the device information (the rotation speed of the compressor 11, the valve opening degree of each valve, and the like) and the like. The inlet density of the outdoor second control valve 17 is calculated based on the detection value (the discharge pressure HP, the refrigerant temperature of the outdoor heat exchanger 14, and the like) of the outdoor sensor 26, and the like.

The controller 70 predicts the inlet pressure of the indoor expansion valve 41 based on the evaporation temperature of the indoor heat exchanger 42, the refrigerant circulation amount of the operating unit, the opening degree (Cv value at the current opening degree) of the indoor expansion valve 41, and the density of the refrigerant at the outlet of the indoor expansion valve 41 (see g in fig. 2). The evaporation temperature of the indoor heat exchanger 42 is calculated based on a detection value of the indoor side sensor 46 (refrigerant temperature of the indoor heat exchanger 42) and the like. In addition, the refrigerant circulation amount of the operation unit is calculated based on the air conditioning capacity of the operation unit. In addition, the density of the refrigerant at the outlet of the indoor expansion valve 41 is calculated based on the enthalpy of the refrigerant at the outlet side of the outdoor unit 10 and the evaporation temperature in the indoor unit 40.

Then, the controller 70 calculates the pressure loss Δ P in the liquid-side communication pipe LC based on the outlet pressure of the outdoor second control valve 17, the inlet pressure of the indoor expansion valve 41, the detection values (the suction pressure LP, the discharge pressure HP, and the like) of the

sensors

26 and 46, and the like (see f-g in fig. 2).

The pressure loss Δ P can be easily calculated by using the detection value of each

sensor

26 or 46, but can be predicted without using the detection value. For example, the pressure loss Δ P can be predicted by the following equation 1, and thus a sensor can be omitted, and accordingly cost control can be achieved.

[ mathematical formula 1 ]

Δ P · pressure loss of liquid side communication piping

G refrigerant circulation volume

Cv value of indoor expansion valve

den · refrigerant density at the outlet of the indoor expansion valve

The controller 70 then proceeds to step S205.

In step S205, if the FF control condition is not satisfied (that is, if the operating capacity does not significantly vary, in this case, NO), the controller 70 returns to step S201. On the other hand, when the FF control condition is satisfied (that is, when the operating capacity has largely changed, YES in this case), the controller 70 proceeds to step S206.

In step S206, the controller 70 executes feed-forward control. Specifically, in the feedforward control, the controller 70 calculates the pressure loss Δ P in the liquid-side communication pipe LC after the operation capacity fluctuation based on the ratio of the refrigerant circulation amount before the operation capacity fluctuation to the refrigerant circulation amount after the operation capacity fluctuation, and the like (see f ″ -g in fig. 6).

The pressure loss Δ P in the liquid-side communication pipe LC after the variation in the operating capacity can be easily calculated by using the detection value of each

sensor

26 or 46, but can be predicted without using the detection value. For example, the pressure loss Δ P can be predicted by the following expression 2, and thus a sensor can be omitted, and accordingly cost control can be achieved.

[ mathematical formula 2 ]

Pressure loss after capacity fluctuation

G refrigerant circulation volume

L. liquid side communication pipe length

D.liquid side communication pipe inside diameter

den · refrigerant density at the outlet of the indoor expansion valve

(since the length and the inner diameter of the pipe do not change, Δ P can be predicted from the circulating amount and the outlet density of the refrigerant)

Then, the controller 70 determines the pressure reduction ratio in the outdoor second control valve 17 based on the calculated pressure loss Δ P, the condensing pressure of the outdoor heat exchanger 14 (see e in fig. 6), and the like, and controls the valve opening degree of the outdoor second control valve 17 so that the inlet pressure of the indoor expansion valve 41 does not change before and after the variation in the operating capacity.

After that, the controller 70 proceeds to step S207.

In step S207, in the case where the FF control completion condition is not satisfied (i.e., in the case where it is not assumed that the risk of a significant increase in the inflow of refrigerant to the operation unit is eliminated, in this case, in the case of NO), the controller 70 stays in step S207. On the other hand, when the FF control completion condition is satisfied (that is, when it is assumed that the risk of a significant increase in the flow of refrigerant into the operation unit is eliminated, YES in this case), the controller 70 returns to step S201.

The same operational advantages as those of the above embodiment can be achieved by the flow of steps S201 to S207 as described above. Further, according to the present example, the pressure loss Δ P in the liquid-side communication pipe LC before and after the fluctuation of the operating capacity is calculated (predicted) in real time, and the valve opening degree is determined by adjusting the decompression ratio of the electrically operated valve that is the target of the feedforward control based on the calculated pressure loss Δ P.

(7-2) modification 2

In the air conditioning system 100, in the feedforward control, as shown in fig. 6, the opening degree of a predetermined motor-operated valve (the outdoor second control valve 17 in the above-described embodiment) disposed in the refrigerant circuit RC is reduced in accordance with the degree of fluctuation of the operating capacity, whereby an increase in the amount of pressure reduction in the indoor expansion valve 41 of the operating means is suppressed, and the generation of noise associated therewith is suppressed.

Here, in the feedforward control, the motor-operated valve for adjusting the opening degree is not necessarily limited to the outdoor second control valve 17. That is, instead of or in addition to the outdoor second control valve 17, other motor-operated valves may be reduced in size, so long as an increase in the amount of pressure reduction in the indoor expansion valve 41 of the operating means is suppressed as shown in fig. 6 when the operating capacity is greatly varied.

For example, in the feedforward control, the opening degree of the outdoor first control valve 16 (corresponding to the "third motor-operated valve" in the claims) may be reduced. For example, in the feed-forward control, the opening degree of the indoor expansion valve 41 (corresponding to the "second motor-operated valve" in the claims) may be decreased. For example, another electrically operated valve not disclosed in fig. 1 may be disposed in the refrigerant circuit RC (particularly, in the flow path on the liquid side of the outdoor heat exchanger 14), and the opening degree of the electrically operated valve may be reduced in the feedforward control. In these cases, too, an increase in pressure of the refrigerant flowing into the operating unit that is maintained in the operating state until the operating capacity changes can be suppressed, and the same operational effects as in the above-described embodiment can be achieved.

In this case, in the feedforward control, any one of the electric valves may be controlled alternatively, or a plurality of the electric valves may be controlled. In this case, the outdoor second control valve 17 is not necessarily required, and may be appropriately omitted, and for example, another mechanism (for example, a pressure reducing mechanism such as a capillary tube) for realizing gas-liquid two-phase conveyance may be disposed instead of the outdoor second control valve 17.

(7-3) modification 3

In the above embodiment, the case where the number of operating means is reduced or increased by a predetermined number (for example, 2) or more during the forward circulation operation and a predetermined period Pt, the FF control condition is satisfied and the feedforward control is executed has been described. However, the FF control condition is not necessarily limited thereto, and may be appropriately changed.

For example, if the number of operating units decreases or increases by a predetermined number (for example, 2) or more in the predetermined period Pt, the FF control condition may be satisfied when the predetermined first state (the state in which the total value of the air conditioning capacity of the indoor unit 40 in which the operating state has changed is equal to or greater than the predetermined reference value SV) is reached. More specifically, if the number of operating units is reduced by a predetermined number or more, the FF control condition may be satisfied when the total value of the air conditioning capacity of the indoor unit 40 whose operating state has changed (the indoor unit 40 whose operating state has changed to the operation stop state) is equal to or greater than a predetermined first reference value SV 1. When the number of operating units is increased by a predetermined number or more, the FF control condition may be satisfied when the total value of the air conditioning capacity of the indoor units 40 whose operating state has fluctuated (the indoor units 40 that have been brought into an operating state from an operation stopped state) is equal to or more than a predetermined second reference value SV 2.

In this case, the operating capacity variation detecting unit 74 may specify the indoor units 40 whose operating states have varied (started/stopped) from the device information, and calculate the total value of the air conditioning capacities of the specified indoor units 40 based on the capacity information. Further, the operating capacity fluctuation detection unit 74 may be configured to establish the FF control flag M9 by determining that the operating capacity of the air conditioning system 100 has greatly fluctuated when the calculated value is equal to or greater than the first reference value SV1 or the second reference value SV 2.

The first reference value SV1 and the second reference value SV2 are values at which, assuming that the variation in the operating capacity has occurred, the noise is likely to increase in the operating means for maintaining the operating state in association with the gas-liquid two-phase conveyance, and the values at which the noise increases in the operating means for the operating state are set as appropriate in accordance with the design specifications and the installation environment. The first reference value SV1 and the second reference value SV2 may be set to the same value or may be set to different values. For example, the first reference value SV1 and the second reference value SV2 are set to 5.0(Kw) (not necessarily limited thereto).

When the FF control condition is set in this manner, if the number of operating units decreases or increases by a predetermined number (for example, 2) or more during the predetermined period Pt, the feedforward control is executed when the predetermined first state (the state in which the total value of the air conditioning capacity of the indoor unit 40 in which the operating state has changed is equal to or more than the predetermined reference value) is reached. As a result, the first control can be executed in the first state (i.e., the state in which the first control needs to be executed in particular) in which the operating capacity of the entire system greatly changes. Therefore, the increase in noise associated with the gas-liquid two-phase conveyance in the operation unit can be more reliably suppressed.

(7-4) modification 4

For example, the FF control condition is not necessarily limited to the case of performing the forward circulation operation, and may be satisfied even in the case of performing another operation of gas-liquid two-phase conveyance.

(7-5) modification 5

In the above embodiment, the case where the predetermined period Pt is set to 30 seconds has been described as an example. However, the predetermined period Pt is not necessarily limited to 30 seconds, and may be longer than 30 seconds or shorter than 30 seconds. For example, the predetermined period Pt may be set to 1 minute or 15 seconds.

In the above embodiment, the case where the predetermined time t1 is set to 1 minute has been described as an example. However, the predetermined time t1 is not necessarily limited to 1 minute, and may be longer than 1 minute or shorter than 1 minute. For example, the predetermined time t1 may be set to 3 minutes or 30 seconds.

(7-6) modification 6

The configuration of the refrigerant circuit RC in the above embodiment is not necessarily limited to the one shown in fig. 1, and may be appropriately changed according to design specifications and installation environments.

For example, the outdoor first control valve 16 is not necessarily required, and may be omitted as appropriate. In this case, the outdoor second control valve 17 may also play a role of the outdoor first control valve 16 during the reverse cycle operation.

For example, the outdoor second control valve 17 is not necessarily disposed inside the outdoor unit 10, and may be disposed outside the outdoor unit 10 (for example, on the liquid-side communication pipe LC).

For example, the indoor expansion valve 41 is not necessarily disposed inside the indoor unit 40, and may be disposed outside the indoor unit 40 (for example, on the liquid side communication pipe LC).

For example, the subcooler 15 and the outdoor third control valve 18 are not necessarily required, and may be omitted as appropriate. Further, a device not shown in fig. 1 may be newly added.

For example, in the refrigerant circuit RC, a refrigerant flow switching unit that switches the flow of the refrigerant flowing into each indoor unit 40 may be disposed between the outdoor unit 10 and each indoor unit 40 so that the forward cycle operation and the reverse cycle operation can be performed individually for each indoor unit 40. In this case, the FF control condition may not necessarily be satisfied in a state where the indoor unit 40 performing the forward cycle operation (cooling operation) and the indoor unit 40 performing the reverse cycle operation (heating operation) are mixed together only in the forward cycle operation. In this case, the electrically operated valve to be controlled may be disposed in the refrigerant flow switching means in the feedforward control.

(7-7) modification 7

In the air conditioning system 100 of the above embodiment, the controller 70 (the device control unit 75) completes the feedforward control when the predetermined FF control completion condition is satisfied after the execution of the feedforward control is started, and the FF control completion condition is satisfied when the predetermined time t1 has elapsed after the execution of the feedforward control. However, the FF control completion condition is not necessarily limited to this, and may be satisfied when another event is triggered. For example, the FF control completion condition may also be satisfied based on the detection values of the

respective sensors

26 or 46 stored in the detection value storage area M2, the device information stored in the device information storage area M3, and/or the input command stored in the command storage area M4, or the like.

(7-8) modification 8

In the air conditioning system 100 of the above embodiment, a plurality of (4 or more) indoor units 40 and one outdoor unit 10 are connected in series or in parallel by communication pipes (GC, LC). However, the number of outdoor units 10 and/or indoor units 40 and their connection method may be changed as appropriate depending on installation environment and design specifications. For example, a plurality of outdoor units 10 may be arranged in series or in parallel. In addition, only one indoor unit 40 may be connected to one outdoor unit 10.

(7-9) modification 9

In the above embodiment, the controller 70 for controlling the operation of the air conditioning system 100 is configured by connecting the outdoor unit control unit 30 and the indoor unit control unit 48 of each indoor unit 40 via the communication line. However, the configuration of the controller 70 is not necessarily limited thereto, and may be appropriately changed according to design specifications and installation environments. That is, as long as the elements (71-77) included in the controller 70 are realized, the configuration of the controller 70 is not particularly limited. That is, some or all of the elements (71 to 77) included in the controller 70 are not necessarily disposed in any of the outdoor unit 10 and the indoor unit 40, and may be disposed in another device or may be disposed independently.

For example, the controller 70 may be configured by another device such as the remote controller 60 or a centralized management device together with or instead of one or both of the outdoor unit control unit 30 and each of the indoor unit control units 48, or one or both of the outdoor unit control unit 30 and each of the indoor unit control units 48. In this case, other devices may be disposed at remote locations connected to the outdoor unit 10 or the indoor unit 40 via a communication network.

For example, the controller 70 may be constituted only by the outdoor unit control unit 30.

(7-10) modification example 10

In the above embodiment, R32 is used as the refrigerant circulating in the refrigerant circuit RC. However, the refrigerant used in the refrigerant circuit RC is not particularly limited, and may be another refrigerant. For example, HFC refrigerants such as R407C and R410A may be used in the refrigerant circuit RC.

(7-11) modification 11

In the above embodiments, the idea of the present disclosure is applied to the air conditioning system 100. However, the present disclosure is not limited thereto, and the present disclosure may be applied to other refrigeration apparatuses (for example, a water heater, a heat pump chiller/heater unit, and the like) having a refrigerant circuit.

(7-12) modification 12

In the above-described embodiment, the idea of the present disclosure is applied to the air conditioning system 100 that performs gas-liquid two-phase conveyance. In this regard, the idea of the present disclosure focuses on suppressing the increase in pressure of the refrigerant flowing into the operation means and the generation of noise associated therewith when the operation capacity is greatly varied during gas-liquid two-phase conveyance (i.e., when the opening degree of the indoor expansion valve 41 of the operation means is large as compared with the case of liquid conveyance).

However, the concepts of the present disclosure do not necessarily preclude application to air conditioning systems that perform liquid transport. That is, in the air conditioning system that performs liquid conveyance, the same problem may occur (although the degree is difficult to increase compared to gas-liquid two-phase conveyance) in association with the case where the operating capacity also greatly fluctuates, and therefore, it is needless to say that the idea of the present disclosure may be applied. That is, in the case of liquid conveyance in which the refrigerant flowing through the liquid-side communication pipe LC is in a liquid state, there is a possibility that the pressure of the refrigerant flowing into the operation means varies (particularly, the pressure of the refrigerant flowing into the operation means increases as the number of operation units increases) and noise is generated in accordance with the variation of the operation capacity. In addition, when liquid is transported, it is conceivable that the outdoor second control valve 17 is not disposed in the refrigerant circuit RC, but in this case, the opening degree of a predetermined electric valve (for example, the outdoor first control valve 16 and/or the indoor control expansion valve 41) may be controlled by feedforward control.

(8)

While the embodiments have been described above, it should be understood that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Industrial applicability of the invention

The present disclosure may be utilized in an air conditioning system.

Description of the reference numerals

10: outdoor unit

11: compressor with a compressor housing having a plurality of compressor blades

12: energy accumulator

13: four-way switching valve

14: outdoor heat exchanger

15: subcooler

16: outdoor first control valve (electric valve, third electric valve)

17: outdoor second control valve (electric valve, first electric valve)

18: outdoor third control valve

19: liquid side stop valve

20: gas side stop valve

25: outdoor fan

26: outdoor side sensor

30: outdoor unit control unit

40(40a, 40b, 40c, 40 d): indoor unit

41: indoor expansion valve (electric valve, second electric valve)

42: indoor heat exchanger

45: indoor fan

46: indoor side sensor

48: indoor unit control unit

60: remote controller

70: controller (detection part, control part)

71: storage unit

72: input control unit

73: mode control unit

74: operation capacity variation detecting section (detecting section)

75: equipment control part (control part)

76: drive signal output unit

77: display control unit

100: air conditioning system

151: main flow path

152: sub flow path

GC (G1, G2 …): gas side communication pipe

LC (L1, L2 …): liquid side communication pipe

M1: program storage area

M2: detection value storage area

M3: device information storage area

M4: instruction memory area

M5: controlling a memory area in general

M6: FF control condition storage area

M7: FF control storage area

M8: control mode discrimination flag

M9: FF control flag

P1-P14: first to fourteenth piping

RC: refrigerant circuit

Documents of the prior art

Patent document

Patent document 1: international publication No. 2015/029160

Claims

1. An air conditioning system (100) that performs a refrigeration cycle in a Refrigerant Circuit (RC) including an outdoor unit (10), a plurality of indoor units (40), and refrigerant communication piping connecting the outdoor unit and the indoor units,

the refrigerant flowing from the outdoor unit to the indoor unit flows into the indoor unit in a gas-liquid two-phase state,

the air conditioning system (100) is provided with:

an electric valve for decompressing the refrigerant flowing through the refrigerant circuit according to the opening degree;

detection units (70, 74) for detecting a change in the number of operating units, which are the indoor units in an operating state; and

a control unit (70, 75) for controlling the state of the electric valve,

the electric valves comprising a first electric valve (17) and a second electric valve (41),

the first motor-operated valve (17) depressurizes the refrigerant so that the refrigerant flowing from the outdoor unit to the indoor unit passes through the refrigerant communication pipe in a gas-liquid two-phase state,

the second motor-operated valve (41) reduces the pressure of the refrigerant flowing from the refrigerant communication pipe into the corresponding indoor unit,

when the detection unit detects that the number of the operation units changes, the control unit executes a first control in which the opening degree of the first motor-operated valve (17) is adjusted to suppress an increase in the pressure of the refrigerant flowing into the operation units,

in the first control, the first control is executed,

the decompression ratio and the opening degree of the first motor-operated valve (17) are adjusted according to the variable operation capacity of the operation unit,

alternatively, the first and second electrodes may be,

the pressure of the refrigerant at the inlet of the second motor-operated valve (41) corresponding to the operation means is predicted, and the opening degree of the first motor-operated valve is adjusted by determining the decompression ratio of the first motor-operated valve (17).

2. The air conditioning system (100) of claim 1,

the refrigerant flowing from the outdoor unit to the indoor unit is delivered in a gas-liquid two-phase state.

3. The air conditioning system (100) of claim 1,

the control unit executes the first control when the detection unit detects that the number of the operating units decreases,

in the first control, the first control is executed,

adjusting the decompression ratio and the opening of the first electrically operated valve (17) on the basis of a control table defining the decompression ratio of the first electrically operated valve (17) according to the magnitude of the varying operating capacity of the operating means,

alternatively, the first and second electrodes may be,

the pressure of the refrigerant at the inlet of the second motor-operated valve (41) corresponding to the operation means is predicted, and the decompression ratio of the first motor-operated valve is determined in real time to adjust the opening degree of the first motor-operated valve.

4. The air conditioning system (100) of any of claims 1-3,

a storage unit (71) for storing capacity information specifying the air conditioning capacity of each of the indoor units,

the control unit executes the first control when the detection unit detects that the number of the operating units has changed, and when the total value of the air conditioning capacity of the indoor units, the operating state of which has changed, is in a first state in which the total value is equal to or greater than a predetermined reference value.

5. The air conditioning system (100) of any of claims 1-3,

the control unit reduces the opening degree of the first motor-operated valve in the first control.

6. The air conditioning system (100) of any of claims 1-3,

further provided with an outdoor heat exchanger (14) disposed in the outdoor unit and functioning as a condenser or a radiator for the refrigerant,

the electric valve includes a third electric valve (16) disposed between the outdoor heat exchanger and the refrigerant communication pipe,

the control unit reduces the opening degree of the third motor-operated valve in the first control.